This application claims priority of international application PCT/IB99/00134 filed Jan. 26, 1999 with priority of RU 98101488 filed Jan. 27, 1998.
The invention pertains to the field of jet technology, primarily to pumping-ejection systems for producing a vacuum.
A pumping-ejection system is known, which has a liquid-gas ejector and a pump. The gas inlet of the ejector is connected to a source of an evacuated gaseous medium, the liquid inletxe2x80x94of the ejector is connected to the discharge side of the pump, an outlet of the ejector is connected to a drainage system (see xe2x80x9cJet Apparatusesxe2x80x9d, book of E. Y. Sokolov, N. M. Zinger, xe2x80x9cEnergiaxe2x80x9d Publishing house, Moscow, 1970, page 215).
The main imperfection of this system is its low efficiency.
The closest analogue of the system introduced in the present invention is a pumping-ejection system having a vacuum separator, a pump, an inlet liquid-gas ejector, a discharge liquid-gas ejector and an outlet separator, wherein the suction side of the pump is connected to the liquid outlet of the vacuum separator, the gas inlet of the inlet ejector is connected to a source of an evacuated gaseous medium, the liquid inlet of the inlet ejector is connected to the discharge side of the pump, an outlet of the inlet ejector is connected to the vacuum separator, the gas inlet of the discharge ejector is connected to the gas outlet of the vacuum separator, an outlet of the discharge ejector is connected to the outlet separator (see RU, patent, 2084707, cl. F 04 F 5/54, 1997).
This pumping-ejection system is intended for producing and maintaining a vacuum, mainly in rectification columns. More intensive operation of the system is achieved because the system incorporates two self-contained stages of evacuation. However, this arrangement with the two self-contained stages of evacuation has some shortcomings: the operational pressure within the second stage is higher than the operational pressure within the first stage, therefore a liquid medium circulating in the second-stage circulation loop is saturated with a solute gas more intensively if compared with a liquid medium circulating in the first-stage circulation loop. Continuous employment of a motive liquid saturated with a gas reduces the efficiency of the second-stage ejector and results in an increase in the energy consumption for providing the required flow rate of gases evacuated from the vacuum separator. Additionally, two independent loops of the motive liquid circulation require two independent pumps for delivery of the motive liquid to the ejectors inlets. This makes transfer of the motive liquid from one circulation loop to another more complex.
The present invention is aimed at attaining more economical operation of the system due to employment of a motive liquid with minimal content of a solute gas in all of the system""s evacuation stages.
This objective is achieved as follows: a pumping-ejection system, which has a vacuum separator; a pump connected through its suction port to the vacuum separator; an inlet liquid-gas ejector, whose gas inlet is connected to a source of an evacuated gaseous medium, liquid inletxe2x80x94is connected to the discharge side of the pump and whose outlet is connected to the vacuum separator; an outlet separator, a discharge liquid-gas ejector, whose gas inlet is connected to the vacuum separator and whose outlet is connected to the outlet separator; is furnished further with a pipe for liquid tapping, which connects the outlet separator with the vacuum separator, and the liquid inlet of the discharge ejector is connected to the discharge side of the pump. The pumping-ejection system can be furnished with an outlet liquid-gas ejector and with a final separator. In this case the gas inlet of the outlet ejector is connected to the outlet separator, the liquid inlet of the outlet ejector is connected to the discharge side of the pump, an outlet of the outlet ejector is connected to the final separator, and the liquid outlet of the final separator is connected to the vacuum separator. In addition, the system can be furnished with a heat exchanger-cooler installed at the suction side of the pump.
It was determined, that the condition of a motive liquid being fed by the pump into the nozzles of the liquid-gas ejectors through their liquid inlets, exerts a significant influence on the performance the of the pumping-ejection system as a whole. The main factor which affects the condition of the motive liquid most of all is the content of a solute gas in the motive liquid.
As it was noted above, in the prototype pumping-ejection system a motive liquid is fed from the outlet separator into the second-stage liquid-gas ejector under a pressure, which is higher than a pressure maintained in the vacuum separator, and this is the cause of a lower capacity of the second-stage ejector. This effect is explained by the fact that the motive liquid always contains a certain quantity of a solute gas and emission of the solute gas from the motive liquid occurs when pressure in the ejector receiving chamber becomes equal to the saturation pressure of the solute gas. Therefore the ejector gas capacity decreases, because, together with an evacuated gaseous medium, the ejector must evacuate the gas evolved from the motive liquid.
In the pumping-ejection system described in the present invention, a motive liquid is fed into the nozzles of all ejectors from the vacuum separator, because prior to feeding the motive liquid into the nozzles of appropriate ejectors, the motive liquid from the separators of the consequent stages is transferred into the vacuum separator, where the lowest pressure is maintained and where the liquid is degassed most effectively. Thus, the motive liquid degassed under a lowest possible pressure is fed into the nozzles of all ejectors. As compared with the prototype system, the pumping-ejection system of the introduced layout ensures a higher gas capacity or less energy consumption in view of equal gas capacity.
Thus, a more economical operation is provided by the described system.